The relates to a method for regulating the conditioning of a gas. It also relates to a device for conditioning a gas implementing this method; it relates more particularly to an adjustable, controllable device for regulating the vapour concentration and the temperature of a gaseous flow.
As is known, in essence, a gas conditioning device comprises in a thermostatted enclosure:
an inlet of gas to be conditioned, PA1 an evaporation and mixing humidifier device, PA1 an outlet of the conditioned gaseous flow. PA1 the temperature of the gas is brought to the desired conditioning temperature, PA1 the gas is saturated by means of a conditioning liquid, PA1 and the saturated and thermally conditioned gas thus obtained is mixed with the said non-saturated nonconditioned gas in a proportion depending on the desired conditioning, consists in saturating the gas in a reduced-pressure environment at a temperature in the vicinity of the temperature for conditioning the gas by atomizing the conditioning liquid brought to a temperature in the vicinity of the temperature for conditioning the said gas in the said reduced-pressure environment. PA1 an inlet of gas at a programmed temperature, connected to a source of the said gas; PA1 a gas humidifier for bringing a conditioning liquid into contact with the gas to be conditioned; PA1 a conditioned gas outlet tubing connecting the outlet orifice of the humidifier to the volume to be conditioned. PA1 a converging region connected to the thermostatted inlet tubing; PA1 a neck, PA1 a diverging region emerging in the vaporization chamber, PA1 a tubing connecting the conditioning liquid and emerging in the neck of the Venturi, PA1 and an outlet orifice disposed above the maximum level of the conditioning liquid in the said vaporization chamber. PA1 the compressed gas is dry compressed air whose source is connected in series to the inlet tubing via a first pressure-reducing valve and then, by a drying means, via a second pressure-reducing valve associated with a valve in order to introduce into the inlet tubing compressed dry air at a constant flow rate; PA1 in a known manner, the heat transfer liquid (advantageously water), of the thermostatted enclosure comprises an electrical resistance element, an agitator, a thermometer and a means for displaying and programming the temperature of the water and of the enclosure, the whole assembly being controllable from the outside; PA1 the means for supplying the vaporization chamber with water to a constant level comprises, outside the thermostatted enclosure and in series, an expansion vessel, a first valve allowing a slight leakage of air, a reservoir of water thermostatted by the water of the enclosure, a controlled second valve and a tubing traversing the thermostatted enclosure connected to an orifice emerging in the vaporization chamber in order to maintain a constant level therein; PA1 the outlet tubing has in series a controllable mixer valve connected to a pipe coil disposed in the thermostatted enclosure; PA1 this mixer valve is associated with a slightly opened valve allowing a slight leakage intended to provide in all cases a minimum flow rate of air in the humidifier; PA1 the constant level vaporization chamber comprises a succession of horizontal parallel grids or plates produced from a thermally conductive material, the said grids or plates then being integral with the vaporization chamber, and comprising a plurality of orifices which are offset from one plate or from one grid to another; PA1 the leaktight humidifier immersed in the enclosure is produced from a heat conductive material and comprises fins for heat exchange with the thermostatted transfer liquid; PA1 the tubing connecting the vaporization chamber and emerging in the neck of the Venturi has opposing orifices disposed horizontally in the cross-section of the neck; PA1 the outlet orifice of the vaporization chamber is connected via a centrifuge-type droplet separator disposed in the enclosure above the said orifice, and whose outlet of saturated gas is connected to the tubing, the separated liquid subsequently returning by another tubing in the conditioning liquid via the orifice located below the constant level.
In document FR-A-2,558,737, a humid gas generating device is proposed in which humidified air is mixed with dry air with a view to producing a humid reference gas, especially for monitoring and calibrating a hygrometer in industrial use, particularly adapted to regulation in the metallurgical industry. According to this document, the thermostatted humidifier is formed by a bubbling chamber partially filled with water to a constant level, connected on the one hand by a diffuser at the inlet of gas to be humidified, and on the other hand to an inlet tubing for water at a constant level and, finally, to an outlet of the humidified gas. This solution is perfectly suitable for low flow rates, especially for calibrating a probe or a hygrometer. However, because of the bubbling technique itself, this device may not be used for conditioning significant volumes, such as rooms, workshops or atomising apparatuses, which require large flow rates, as such flow rates are not compatible with a system for humidifying by bubbling.
Moreover, it is increasingly sought to produce conditioned air whose moisture content is controlled to within 1%, even to one part in a thousand. Such is especially the case for measurement apparatuses.
There has also been proposed, for example in document WO 88/01195, a humidifier device in which the humidification is obtained by atomizing a liquid into a mixing chamber, the said liquid being atomised in contact with an air inlet source. Thus, a gas which is humidified, even saturated, is indeed obtained, but with a very low efficiency, the mostly adiabatic evaporation causing the cooling the air-droplets mixture in the mixing chamber and, furthermore, the temperature of the atomized liquid is not regulated so that the gas is only partially conditioned.